I've written before about the AT&T MicoCell, a device that costs between $50 and $150 (depending upon whether you also purchase extra services) that uses your existing high speed internet to give you a bubble of excellent AT&T 3G service in about 40 feet each direction from the placement of the MicoCell. If you have trouble getting a good AT&T signal at your home or office, this may be a solution. You don't have to purchase anything other than the unit itself, but if you pay $20 a month ($10 if you have AT&T internet service) the calls that you make on the MicroCell don't count against your monthly minutes.
I haven't had the opportunity to try a MicroCell myself yet, but I mention the MicroCell today because Rachel Metz of the Associated Press just posted a great hands-on review of the product. If you are thinking about purchasing a MicroCell, read this review. Dan Moren of Macworld also recently wrote about the MicroCell, although it doesn't appear that he had a chance to test it himself, and Brian Iam and Matt Buchanan of Gizmodo penned this review a few weeks ago.
All of the reports that I have seen, including these recent reviews, anecdotal postings on online forums, and reviews from folks in places like North Carolina where the product was first tested last year, have been very similar: the product seems to work great, with the only major complaint being the need to pay more to AT&T for better service.
UPDATE: Lawyer and iPhone app developer Cliff Maier posted a comment to this original post that I thought was interesting enough that it should be elevated to this post itself: